Researchers have developed a tiny flower-shaped magnetic structure that can dramatically boost local magnetic fields and improve the performance of magnetic sensors.
The magnetic microstructure of the nickel-iron alloy leads to a compression of the field lines in the center. Image Credit: A. Palau/ICMAB
A flower-shaped structure just a few micrometers wide, made from a nickel-iron alloy, can locally concentrate and enhance magnetic fields. The strength of this effect can be tuned by adjusting the geometry and number of “petals.”
Developed by Dr. Anna Palau's team at the Institut de Ciència de Materials de Barcelona (ICMAB), in collaboration with partners from the CHIST-ERA MetaMagIC project, this magnetic metamaterial was recently studied at the BESSY II synchrotron with Dr. Sergio Valencia.
The structure has potential applications in improving magnetic sensor sensitivity, reducing energy consumption for generating local magnetic fields, and enabling high-field magnetic studies at the PEEM experimental station.
Under a scanning electron microscope, the metamaterial resembles miniature flowers. The petal-like structures are thin strips of ferromagnetic nickel-iron alloy. These “microflowers” can be fabricated in a variety of shapes, with different inner and outer radii, as well as varying numbers and widths of petals. This specific design channels the field lines of an external magnetic field toward the center of the structure, significantly amplifying the local magnetic field.
What Are Magnetic Metamaterials?
Metamaterials are artificially produced materials with microstructures whose dimensions are smaller than the electromagnetic or thermal waves they are designed to manipulate.
Anna Palau, Institut de Ciencia de Materials de Barcelona
Her research focuses on magnetic microstructures that could be applied in data storage, information processing, biomedicine, catalysis, and magnetic sensing. By amplifying magnetic fields at a specific point, these materials can greatly enhance the performance of magnetic sensors.
Mapping Magnetic Domains at BESSY II
Dr. Palau, together with her student Aleix Barrera and Dr. Sergio Valencia, explored this concept at the XPEEM experimental station at BESSY II. They positioned a cobalt rod in the center of various microflower designs to act as a magnetic field sensor, then mapped the magnetic domains inside the rod.
By adjusting the geometric parameters such as shape, size, and number of petals, the magnetic behavior can be switched and controlled.
Dr. Sergio Valencia, Institut de Ciencia de Materials de Barcelona
This fine-tuning can lead to magnetoresistive sensors that are over 100 times more sensitive than current designs.
New Options, Also for Experiments at XPEEM
This approach not only holds promise for improving compact magnetic sensors but also for developing multifunctional magnetic components. In experimental setups like XPEEM, where magnetic fields typically limit electron imaging due to deflection, these microstructures offer a workaround.
Our experimental system is a photoemission electron microscope, so magnetic fields deflect the electrons and make the experiments difficult. The maximum magnetic field we can normally apply for imaging is about 25 mT. With the magnetic field concentrator, where the field is only locally enhanced, we can easily achieve fields five times higher.
Dr. Sergio Valencia, Institut de Ciencia de Materials de Barcelona
This means researchers can now explore magnetic systems under previously inaccessible conditions—an exciting development for materials science and experimental physics alike.
Journal Reference:
Barrera, A., et al. (2025) On-Chip Planar Metasurfaces for Magnetic Sensors with Greatly Enhanced Sensitivity. ACS Nano. doi.org/10.1021/acsnano.5c00422.